There were several comments throughout this thread that temperature was the key for the transmission fill.
Certainly that is, but getting the fluid level correct, trans fluid temp in range and vehicle running in PARK. That ensure the fluid in the trans is at the right temp and density (not viscosity) and that the pump, torq converter and other components are full. Please do your research, if you don't fill in this fashion the trans is underfilled and could cause you problems down the road.
I did mine last a year ago and I pumped in over another bottle. If you remove the fill plug before the drain plug, you should get over a litre of fluid out; if you don't then it is not full enough.
The procedure on ZF's website is the correct one to follow, as well as the change interval.
https://aftermarket.zf.com/sea/en/af...on-oil-change/